HSDPA Inter-Frequency Load Sharing › This feature allows to divide HS users between several HS carriers based on number of HS users on each carrier f3 › MultiCarrier, MIMO and EUL capabilities are considered in the loadsharind decision f2 › The feature is triggered when going from a non-HS configuration to an HS configuration both at RAB establishment and Channel Upswitch f1 W10B HSPA IFLS | ELUIESC | Page 0 Change in Parameters › It is possible to define up to 5 coverageRelations out from each utranCell › The coverageRelation MO is extended with 3 on/off parameters: – hsCellSelection: indicates if the coverageRelation can be used for HS cell selection (can be set to ON in max. one coverageRelation per utranCell) – hsLoadSharing: indicates If the coverageRelation can be used for HS loadsharing – dchLoadSharing: indicates if coverageRelation can be used for DCH loadsharing › The hsPathlossThreshold parameter in coverageRelation is replaced with a pathlossThreshold parameter in utranCell W10B HSPA IFLS | ELUIESC | Page 1 HSDPA IFLS Sequence (1/2) 1. Trigger point at RAB Establishment or Channel Upswitch (for applicable transitions) 2. Feature licence check and feature active check (hsIflsThreshUsers > 0 in current cell) 3. HSDPA IFLS coverageRelation and band filtering check: There must be at least one HSDPA inter-frequency loadsharing candidate cell defined out from the current cell in a frequency band supported by the UE › If conditions 1-3 are fulfilled the feature HS IF loadsharing replaces the HS cell Selection feature › If conditions 1-3 are not fulfilled the feature HS IF loadsharing is not triggered and HS cell Selection may still be triggered W10B HSPA IFLS | ELUIESC | Page 2 HSDPA IFLS Sequence (2/2) 4. PathLoss check: If the initial state is on SRB or DCH (i.e. not FACH) then a pathloss check must be passed before a blind IFHO can be triggered. If the pathloss is too high then RAB setup (or channel upswitch) continues in the current cell 4. Target cell is selected from a set of appropriate candidate cells 5. If the selected target cell is different from the current cell then a Blind IFHO or a reconfiguration from FACH is performed 6. RAB Establishment or Channel Upswitch continues in target cell W10B HSPA IFLS | ELUIESC | Page 3 Triggering Control › The HSDPA inter-frequency load sharing feature can be triggered when going from a non-HS configuration (and also from SRB on HS) to an HS configuration at either RAB establishment or Channel Upswitch › The HSDPA IFLS is not triggered at RRC setup › The decision on when to perform load sharing is controlled by the ‘iflsMode’ Cell parameter which can have any of the following settings: – RAB_EST: Trigger at RAB establish only – UPSWITCH_ATT: Trigger at upswitch attempts from URA/FACH or DCH caused by channel switching. – RAB_EST_OR_UPSWITCH_ATT (Default): Trigger both a RAB establishment and at upswitch attempts. W10B HSPA IFLS | ELUIESC | Page 4 Target cells for HSDPA IFLS › The initial set of cells to be considered for the HS RAB Est. or Upswitch will be those (source cell and HS IFLS coverage related) with the highest capability (HS/EUL/MIMO/MC) that the UE supports (source cell might thus be excluded at this step) › From that initial set, the following coverage related candidates will be excluded: – Those in frequency bands not supported by the UE – Those in “HS-DSCH congested” state – Those for which no_of_HS_users >= hsdpaUsersAdm – Those for which no_of_serving_cell_EUL_users >= eulServingCellUsersAdm when target configuration includes EUL › If the resulting set is empty the connection continues in current cell W10B HSPA IFLS | ELUIESC | Page 5 MC MC EUL R99 f4 f3 f2 f1 Target Cell Selection a) If the source cell is the only remaining candidate in the list then the connection continues in that cell b) If the source cell is not the only remaining candidate but the number of serving cell HSDPA users in the current cell is lower than a configurable threshold then the connection continues in the current cell. Otherwise the coverage related cells can be considered hsIflsThreshUsers (0 to 100 %, eg. 50 %) hsdpaUsersAdm (0 to 1000, eg.10) Source (f1) no_of_HS_users (eg. 6) no_of_HS_users (6) > 5 => consider coverage related cells c) If the source cell does not remain in the list then a coverage related cell is selected regardless of the source cell load. If a coverage related cell is they only remaining candidate then that cell is selected as target cell W10B HSPA IFLS | ELUIESC | Page 6 Target Cell Selection › When several cells can be considered for target cell then decision is based on the available resources on each of them: RR = hsdpaUsersAdm – no_of_HS_users – (hsIflsMarginUsers/100 * hsdpaUsersAdm) Where hsIflsMarginUsers can be used to to balance the load between cells no_of_HS_users (eg. 6) RRcell hsIflsMarginUsers (0 to 100 %, eg. 25 %) › Cells with RR <=0 are excluded and If the source cell is still among the considered cells then the list is further filtered excluding coverage related cells that do not fulfill the load hysteresis condition: (RR in candidate cell) > (1 + iflsHyst/100) * (RR in current source cell) › If no cell remains the connection continues in current cell. Otherwise the cell among the remaining candidates with the highest RR is selected as target cell for the new configuration W10B HSPA IFLS | ELUIESC | Page 7 HS IFLS Considerations › If the blind IFHO attempt is blocked by admission control or fails and the UE returns to the source cell without dropping, the RAB reconfiguration that triggered the loadsharing continues in the source cell. Only one attempt to do blind IFHO is made › When the UE has been redirected to the new carrier retry cases for lower rates can be triggered if blocked by admission control. These retries do not trigger any new loadsharing attempts › Inter-frequency loadsharing relations should only be defined between cells that have the same coverage or from a smaller to a larger cell › Loadsharing only applies to Ues in SRNC cells since cell load information cannot be read over Iur (3GPP). For Iur case HS cell selection is triggered › HS Loadsharing is not performed when SRB-on-HS is setup from idle (trigger only at RAB establishment or Channel Upswitch) W10B HSPA IFLS | ELUIESC | Page 8
